Tuesday, February 8, 2011

3, 6, 8, 11, 14, 17, 19, Hike!

Happy Adar I.

Adar I you say?

Yes, we’re in a leap year, didn’t you know?

Leap year?

Ok, let’s start at the very beginning… It’s a very good place to start…

The Torah indicates that we can number our weeks by seven days, as in Genesis, God created the world in six days and rested on the seventh. The Torah also indicates that we can number our months by the moon, celebrating the new month with the beginning of the new moon, and our festivals often are celebrated starting on the full moon. And the Torah indicates that we should number our years in order to keep track of the age of people, trees, and when we should celebrate the jubilee year. In addition the Torah indicates proper seasons for our festivals, such as the spring for Pesach, and the fall harvest for Sukkot.

This presents an obvious problem of how to create a proper calendar. Jews need to be able to keep track of the lunar calendar, for when new months occur, as well as dates for festivals, but we also need to keep track of the solar calendar, because those festivals are agricultural in nature, and therefore based on seasons. So, how do we reconcile both ways of keeping track of time?

The solar cycle is 365.24 days in length, and can be easily divided in to 12 equal portions of 30.4 days. In order to remove the .4 of a day each month and the .24 of a day each year, the months were divided up slightly unevenly, with 7 months of 31 days, 4 months of 30 days, and one month of 28 days which receives an extra leap day every four years. By comparison, the lunar cycle is 29.5 days, and a month is generally considered as having either 29 or 30 days depending on which evening the new moon is sighted. Creating a year out of 12 lunar cycles creates a lunar calendar of 354 days, which is 11 days shorter than the solar calendar year. In order to keep our seasonal festivals from sliding around throughout the solar year, and therefore mismatching with the seasons, Jews needed to create a way to compensate for the difference between the lunar and solar cycles.

Necessity being the mother of invention, the concept of the Jewish leap year was born.

Way back in time, Jews were dependent on the Sanhedrin (the Jewish Supreme Court) to keep track of the calendar. Every month at the new moon, the Sanhedrin would hear testimony from witnesses who claimed they had observed the new moon in the night sky. When the court decided that they had two reliable witnesses who both confirmed the new moon on the same night, they would declare the new month, and messengers would be sent out to every community to convey the declaration.

Some years, the Sanhedrin would have concerns about pilgrims being able to arrive in Jerusalem in time for the celebration of Pesach (one of three pilgrimage festivals, and often a time that a census would be taken) due to the weather. We know now that this was that the Sanhedrin was noticing the subtle shift in seasons due to the mismatch of the solar and lunar cycles, and were concerned that pilgrims would have difficulty traveling during the rainy season. The Sanhedrin would then declare a leap year, and add an extra month (Adar II) to the calendar, prior to Nisan, thus delaying the arrival of Pesach by 30 days, giving the pilgrims more time to begin their travels.

Around 350 C.E. the Sanhedrin decided to codify the Jewish calendar, thus replacing the constant declarations of new moons and leap years, with a standardized and predictable calendar. Months were given standard lengths of 29 or 30 days based on the recorded observational history of hundreds of years of new moon declarations (and because it’s just not practical to have one day belonging to two months). With this change in calendar, the Rabbis switched their previous practice and codified that Adar I would be considered the inserted leap month, and Adar II would be considered the “real Adar” when it came to observing festivals, and dates of birth and death. Thus, in the modern day, we celebrate Purim, birthdays, and Yahrzeits that occur in Adar during a non-leap year, during Adar II in a leap year. (Conversely, any such dates that occur in either Adar I or Adar II during a leap year would be celebrated during Adar in a non-leap year.) Though, because of the tradition of increasing joy during the month of Adar, the Rabbis began the practice of celebrating Purim Katan (little Purim) during the month of Adar I.

Leap years were codified to occur across a cycle of 19 years, on the years 3, 6, 8, 11, 14, 17, and 19. This cycle allows each lunar month to more or less match up with its solar calendar equivalent each year, keeping the festivals in their respective seasons. Without this cycle of leap years, about every three years the festivals would slip backwards by an entire month.

The codified Jewish calendar also contains three types of years: chaser (deficient) containing 353 days in a non-leap year, and 383 days in a leap year; kesidrah (regular) containing 354 days in a non-leap year, and 384 days in a leap year; and shalem (complete) containing 355 days in a non-leap year and 385 days in a leap year. During a kesidrah year, all of the Hebrew months contain their normal number of days. During a chaser year the month of Kislev loses a day. During a shalem year the month of Cheshvan gets an extra day. These adjustments allow the Jewish calendar to adjust slightly in order to keep the observance of Yom Kippur from occurring adjacent to Shabbat (due to the inherent difficulty in coordinating fasting with subsequent Shabbat observance).

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Fun with Math! You can figure out if a Hebrew year is a leap year by dividing the year by 19. If the remainder is 3, 6, 8, 11, 14, 17, or zero, then the year is a leap year!

Being born in a leap year has its curiosities:
A child born on the 20th of Adar I in a leap year, will have her Bat Mitzvah after her younger friend who was born the same year on the 5th of Adar II if their B’nai Mitzvot fall during a non-leap year.

Muslims follow solely the lunar calendar for their festivals. Because of this their holidays shift around the secular calendar every year. A holiday that was in the winter this year will be celebrated in the fall in 9 years and the summer in 18 years.

Besides being concerned about travelers becoming delayed during the rainy season, the Sanhedrin were also concerned that Pesach was celebrated in its proper season, since it is also known as Chag HeAviv (the festival of spring). The leap month would be added if the crops and livestock were not sufficiently advanced enough for it to be considered spring.

A leap year is referred to in Hebrew as Shanah Me'uberet, literally: a pregnant year

If you are musically inclined, you may find it helpful to remember the pattern of leap years by reference to the major scale: for each whole step there are two regular years and a leap year; for each half-step there is one regular year and a leap year. This is easier to understand by looking at a piano or keyboard.

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